Deodorization of oils



Feb. 15, 1949. K. McCUBBlN El AL DEODORIZATI'QN OF OILS Filed Oct. 26, 1946 T0 VqC. APE

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7'0 PUMP Patent Feb. i949 naonoarza'rron or ores Delaware Application owner 26, 1946, Serial No. 705,836 3 Claims. (01. 202-46) This invention relates to an improved method and apparatus for the continuous deodorization of fatty materials. More particularly, it pertains to a method and-apparatus for the continuous distillatory deodorization of fatty materials, i. e., deodorization brought about by scrubbing the fatty materials with steam or equivalent inert gas at reduced pressure and elevated temperature. v

The following substances, among others, are designated by the herein used expression fatty materials: glyceride oils and fats of animal, vegetable, and synthetic origin; hydrogenated fatty acid glycerides; the higher molecular weight fatty acids; and the so-called superglycerinated fats and oils, namely, mono glycerides and diglycerides of the higher fatty acids.

Continuous distillatory deodorization of fatty materials is conventionally carried out in columns similar to those used in the fractional distillation of liquids. The column, or tower, is equipped with bubble cap plates or equivalent means to provide intimate contact between descending liquid and ascending vapor, and it is operated under vacuum. Suitably heated fatty material, in liquid condition, admitted at a regulated rate to the column near its top flows downwardly by gravity, while steam, usually in a superheated condition, admitted to the column near its bottom at a controlled rate, flows upwardly. The admitted steam, together with the volatilized odorous materials from the fatty liquid, is withdrawn from the top of the column by suitable evacuating means.

It is also conventional to subject the fatty tinuous distillatory deodorization of fatty mamaterial thus deodorized to a second continuous maintaining lower pressure in the second column for scrubbing purposes in the first column.

A principal object of this invention is to reduce the cost of continuous distillatory deodorization of fatty materials, principally by reducing the consumption of steam or equivalent gas.

Another object of the invention is to improve I the deodorization of fatty materials at a given consumption of steam or other scrubbing gas. Still another object of the invention is the provision of improved apparatus for the contypes.

terials in accordance with the method principles of the invention. I

Additional objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combinations of elements and arrangement of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of the application of .which will be indicated in the claims.

A preferred apparatus for carrying out our improved deodorizing method comprises a plurality of vacuum chambers or zones connected in series with steam vacuum jets for inducing the interchamber flow of gaseous products toward the starting chamber, i. e., the chamber which first receives the fatty material to be deodorized, and also connected in series with pipes to provide for countercurrent interchamber flow of liquid fatty material. Each interconnecting steam jet aspirates steam and volatilized impurities from the top of a chamber through a suitable pipe and discharges these gases, together with its own operating steam into a pipe that enters an adjoining chamber at a point .near its bottom. The finishing chamber, the

last in the series through which the fatty material flows, is maintained at the lowest pressure. The starting chamber is maintained at the highest pressure. can be operated at such pressures that the fatty material enters chambers of successively diminishing pressure as it flows through the apparatus. Each chamber contains means for providing intimate contact between steam and fatty material. Conventional means for this purpose are bubble cap trays and packings of various An adjoining pair of the vacuum chambers preferably are placed at suitably different levels so that the fatty material can flow by gravity from the bottom of a high pressure chamber into the top of a low pressure chamber. A pair can also be on the same level. In the latter case the fatty material must be pumped from the bottom of one chamber into the top of the other. Each vacuum chamber may have an inlet pipe near its bottom for admitting scrubbing steam in addition to that discharged into the chamber by an interconnecting steam jet. The starting vacuum chamber, 1. e., the one the fatty material enters first, has an outlet pipe at its top connected to an evacu- Intermediate chambers.

ating means not associated with another vacuum chamber. The finishing chamber has a pipe leading from its bottom to a pump or equivalent means for removing the deodorized fatty material. The pipes for transferring fatty material from the bottom of one chamber to the top of another have goosenecks or bends in them that provide enough hydrostatic head of liquid fatty material to balance the difference in pressure between the two chambers. Means for heating the fatty material as it flows through the pipe from one chamber to the other are provided. This may comprise, for example, a Jacket surrounding a section of the pipe near the pointjwhere it enters the low pressure chambet, and a suitably heated fluid flowing through the Jacket.

The present invention is based in part upon the discovery that the steam or equivalent gas used for deodorizing purposes in a low pressure chamber of the multi-chamber continuous deodorizing process described above may be advantageously re-used for deodorizing oncoming fatty material in a high pressure chamber. That is, this steam or equivalent gas, despite its content of volatile odorous materials acquired in the low pressure chamber, possesses a substantial capacity for supplementing the vapor pressure of similar but more volatile impurities in the fatty material flowing through the high pressure chamber. Thus, it is capable of assisting in the removal of the more volatile impurities in the latter chamber.

From theoretical considerations, it is recognized that the odorous impurities distilled from the fatty material in the low pressure chamber, being less volatile than those removed in the high pres-sure chamber, would be expected to condense in the fatty material flowing through the latter chamber, owing to the higher pressure therein. This argues against the utility of reusing the scrubbing gas at higher pressure. Despite these considerations, however, distinct improvements in the quality and economy of continuous distillatory deodorization will be obtained by properly applying the principles of this invention. V e

A possible explanation for the unexpected benefit obtained by re-using the deodorizing gas at higher pressure according to theprinciples of this invention is that equilibrium volatilization of the impurities is not obtained in the high pressure chamber. That is to say, appreciable quantitles of impurities that possess substantial vapor pressures under the pressure and temperature condition-s of the high pressure chamber pass into the low pressure chamber. Such impurities, when volatilized in the low pressure chamber and carried into the high pressure chamber, will not condense and be absorbed in the fatty material fiowing through the latter chamber. In connection with this possible explanation for one of the advantages of our invention, it is to be pointed out that equilibrium volatilization of the impurities may be inherently very difficult to obtain when commercially feasible rates of flow of fatty material through the column are employed. This follows from the fact that a considerable pressure drop exists from top to bottom of the column. This is due to the resistance offered to the upward flow of gas through the packing or plates. When bubble cap plates are used, most of the pressure drop is due to the cumulative hydrostatic heads of the liquid layers on the bubble cap plates. The pressure on the fatty material is constantly increasing as the latter flows down through the column, and consequently very little time is afforded for equilibrium volatilization of impurities at a given pressure.

Our invention is based also in part upon the use of a part of the exhausting steam or gas for deodorizing purposes. This principle is new to the continuous distillatory deodorization of fatty materials, and is especially advantageous when combined with re-use of deodorizing gas at higher pressures, as will be explained hereinafter.

The equivalent expressions "exhausting steam and "exhausting gas as used herein refer to the steam or equivalent gas used to maintain reduced pressure in various parts of the deodorizing rials in that equipment assembly.

equipment. Vacuum is commonly obtained by applying the compressed gas to suitably designed Jets. The compressed gas can also be used to operate piston and rotary type vacuum pumps.

The objects of our invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawing which illustrates diagrammatically a preferred apparatus embodied by the invention. The drawing represents an equipment assembly suitable for use in the application of our invention. It also exhibits the flow of process vmate- It is to be pointed out, however, that the drawing is illus-- trative only, and that the invention is not to be construed as limited to the exact features of the drawing.

The single figure of the drawing is a diagrammatic elevational view, mostly in section, of one form of apparatus suitable for operation of our improved deodorizing .method. The fatty material to be deodorized flows into the top bubble cap tray of column I through the feed line. Immediately prior 'to flowing into column i, the feed material, is preferably, but not necessarily, heated and deaerated. The purpose of heating the feed is to promote volatilization of its impurities when exposed to the vacuum and the scrubbing as in column I, and the purpose of removing its air and other dissolved gas is to reduce the load on the apparatus that maintains the desired vacuum in the column. Deaeration and preheating of the feed can be conveniently accomplished by heating the fatty material to the desired temperature and spraying it into a vacuum chamber. This has the added advantage of removing some of the lower boiling odorous constituents. In case the feed cools too much during the vacuum-spray treatment or before it reaches column I, it may be reheated by a heat exchanger before it enters the column. The fatty material should not be heated so hot that it is decomposed or otherwise undesirably altered.

Column l contains a series of bubble cap trays 2 equipped with conventional bubble caps 3 and downspouts 4. The liquid fatty material admitted to the top bubble cap tray by means of a feed pipe 5 covers the tray to such a depth that it overflows through the downspout 4 of that tray onto the next lower tray, then through the downspout of that tray onto the succeedingly lower tray, and thus it flows through the entire column. Meanwhile, steam entering the column near its bottom through either pipe 6 or 1, or both, flows upwardly through the .column and is exhausted through an outlet pipe 8 to a vacuum pump. The steam flows upwardly through the stems of the bubble caps, which pierce the'trays, and out from under the edges of the caps, bubbling through the layer of liquid on the tray as it does so. Steam does not pass upwardly through the downspouts because the bottoms of all the spouts are sealed with liquid.

The vacuum steam distillation of the fatty material in column I volatilizes a large proportion of the odorous impurities that are exhausted with the steam through the outlet pipe 8. The partially deodorized product flows from the bottom of column I through a pipe 9, rises in a gooseneck' I 0, and flows into the top bubble cap tray of column II through an inlet pipe I2, passing through a heater I3 on the way. The purpose of the heater I3 is to reheat the fatty material, if desired, before it enters column II. Ordinarily, some cooling of the preheated feed occurs as it passes through the first column.

Column II is similar in construction to column I. It is equipped with a series of conventional bubble cap trays, a bottom outlet pipe I4 for delivering the finished deodorized product to a pump, an inlet pipe I5 for delivering steam to the column at a point below the bottom bubble cap tray, and a top outlet pipe I6 for delivering the steam and volatilized impurities to a steam jet evacuator IT. The Jet evacuator is operated with high pressure steam obtained through a pipe I8, and it exhausts into the pipe I which leads into the bottom of column I at a point below its bottom bubble cap tray.

In a typical operation of the illustrated apparatus, a moderately low pressure of to mm. of mercury absolute is maintained at the top of column I I. These pressures are maintained while fatty material is flowing through the columns and steam is entering them at pipes I6, I and I5. Naturally, the admission of steam. to the columns has to be adjusted to the capacity of the evacuating means in order to maintain the desired low pressures.

The difference in pressure between the bottom of column I and the top of column II is automatically maintained by the hydrostatic head of liquid provided; for example, by the gooseneck I0. Other equivalentmeans may be used for maintaining the pressure difference between chambers, or columns. I

Any fatty material entrained in the vapor issuing from column I through the pipe 8 will be separated from the vapor by the catchall 20 and 6 tion by about 20 per cent. This is a very important saving because steam cost is a substantial item in the operating cost of deodorizers.

It will be apparent that our invention provides for an improved continuous distillatory deodorization of fatty materials in two or more zones of successively reduced pressure. Aside from providing multiple tower sections, vacuum Jets, heaters, lines, etc., deodorization in multiple zones of diminishing pressure has a distinct advantage over the conventional continuous deodorization in a single column or zone. In a single column, owing to the pressure drop therein, the fatty material enters at the region of lowest pressure and leaves at the region of highest pressure. Under these conditions, the fatty material, as it flows down through the column, enters regions, that are less and less favorable for the removal of the higher boiling, less volatile impurities. By breaking the column into sections or zones, and maintaining them at successively reduced pressures, it is possible to obtain, in effect, a reversal of the pressure gradient in. a single column. This has the very great advantage that it subjects the less volatile impurities to increasing tendency to distill as the fatty v matreial flows through the apparatus.

returned to the feed line through the conduit or pipe 2|.

The following table illustrates the steam-saving advantage of our improved process over the conventional continuous process using a single column. The listed steam consumptions are those required to deodorize 1000 pounds of fatty Conven- Improved tional Con- Continuous tinuous Deodorizer Deodorizer Steam used on external jets ibs 220 154 Effective deodorizing steam. 110 110 Total steam used 330 Pressure, top of column... 3. 4 25 Pressure, bottom of colum 2i. 6 3

Our improved process reduces steam consump- Our invention is especially well adapted to the use of jets for providing the pressure differences between zones or chambers. The steam, or equivalent gas, used in ajet to maintain a given pressure in a zone can be exhausted into a zone of higher pressure to scrub or help deodorize the fatty material flowing through that zone. This jet steam, or gas, will be mixed with the. volatilized impurities and scrubbing gas introduced into all the zones of higher pressure. But, as

pointed out above, the scrubbing gas from zones of low pressure can be advantageously re-used for deodorizing purposes in zones of higher pressure.

It is not necessary that the deodorizing chambers or zones consist of separate vessels or columns as indicated in the drawings. They may, for example, be built into a single column or vessel with the necessary jets (or equivalent means) and 011 lines built into the plate sections or interzone partitions.

It is to be understood that the time, temperature, and pressure conditions of our process can be varied over wide ranges to adapt them to the kind of material being deodorized and to the degree of deodorization desired. Such variat onsv are well known to those skilled in the art. Rate of flow of fatty material through the deodorization apparatus, number of pressure stages or zones employed, the quality and amount of steam used for scrubbing purposes alone, and the extent of feed preheating between deodorizing stages can also be varied over wide limits.

Although it is possible to regulate the action of the vacuum jets between deodorizing sta es so that all the stages or chambers operate under the same pressure, thus creating the effect of a single deodorizing column without pressure drop, we prefer to operate the jets sothat the fatty material enters chambers of successively reduced pressure as it flows through the apparatus. As explained above, this promotes the removal of the less volatile odorous impurities.

Although vacuum jet pumps are the preferred means for maintaining differences in pressure between the treating chambers and inducing an opposing interchamber flow of gaseous products,

other equivalent means may be used. Examples of such equivalent means are mechanical vacuum ,to operate the between-chamber evacuating means, the addition of such extra scrubbing gas to the flnishingchamber alone is usually willcient.

Since certain changes in carrying out the above process and in the constructions set forth, which embody the invention may be made without departing from its scope, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also tobe understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described our invention what we claim as new and desire to secure by Letters Patent is:

1. In a continuous distillatory process fordeodorizing fatty material, wherein the fatty material is contacted with a deodorizing gas in zones of successively diminishing pressure, the improvement which comprises conveying the spent deodorizing gas from a zone of lower pressure to a zone of higher pressure at a temperature at least as high as the temperature of the gas leaving the zone of lower pressure and bringing the conveyed gas into contact with the fatty material in the zone of higher pressure, whereby the capacity of the conveyed gas for deodorizing fatty material at higher pressures is utilized.

2. In a continuous distlllatory process for deodorizing fatty material, wherein the fatty material is contacted with a deodorizing gas in zones of successively diminishing sub-atmospheric pressure, and wherein the sub-atmospheric pressure of at least one zone, other than the zone of highest pressure, is maintained at least in part by means of an evacuator operated with a gas adapted to the deodorization of fatty material, the improvement which comprises conveying the spent gas from said evacuator to a zone of higher pressure and bringing the conveyed gas into contact with the fatty material therein at a temeperature at least as high as the temperature'of the gas leaving the evacuator.

3. In a continuous distillatory process for deodorizing fatty material, wherein the fatty material is successively subjected to the action of a deodorizing gas in separate zones, whereby fatty material of successively increased degrees of deodorization is produced, the improvement which comprises conveying the spent deodorizing gas from a zone yielding fatty material of a given degree of deodorization to a. zone yielding fatty material of a lesser degree of deodorization at a temperature at least as high as the temperature of the gas leaving the former zone and bringing the conveyed gas into contact with the fatty material of said last named zone.

KEATQR McCUBBIN. CHARLES E. MONICAL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

